Rise of Humans

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Hello, I'm Greg Jenner, host of You're Dead to Me, the comedy podcast from the BBC that takes history seriously.

Each week, I'm joined by a comedian and an expert historian to learn and laugh about the past.

In our all-new season, we cover unique areas of history that your school lessons may have missed, from getting ready in the Renaissance era to the Kellogg Brothers.

Listen to You're Dead to Me Now, wherever you get your podcasts.

It's the ancients on history hit.

I'm Tristan Hughes, your host.

Today we're covering the rise of humans.

Yep, that's right.

Human evolution.

It's a story that stretches back some 7 million years, one that begins with ancient apes and ends with us, with many different species of early humans emerging and disappearing in between.

The story of human evolution is one still shrouded in mystery.

Not only is the fossil record for early humans extremely limited, but so much of it is still debated.

Including the all-important question, why did early humans, or hominins, why did they become bipedal?

How did they evolve from long-armed tree dwellers to two-legged runners?

These radical changes in bodily structure that have occurred over millions of years.

Joining me to talk through this evolution story is a fan favourite of the podcast, Dr.

Henry G.

Henry has been on the podcast before to talk about both the origins of life on Earth and the dinosaurs.

Quite a few of you have been clamouring for us to have him back on the show, and I'm delighted to announce his return to talk about the fascinating story of the rise of humans.

Henry, welcome back to the podcast.

It has been too long.

Thank you very much, Kristen.

We've done top five dinosaurs.

We've done the wonderful story of the origins of life on earth.

And this feels like another story, kind of the rise of humanity.

And Henry, this is a story, I mean, to start with, it takes us back more than five, six, seven, eight million years.

There's a lot of history and ancient history and prehistory to cover here.

Yep, that's right.

And the human history, well, ancient history has a very, very long run-up.

I mean, recorded history is barely 5,000 years, but this one goes into 98% of human history, which has no written record.

And we just pick up from fossils and other scraps of information that we can tell from the rock.

And to tell the story of human evolution, as I said, we're going to be covering several million years of history.

You mentioned fossils.

How rich a record do you have?

for studying human evolution?

Do you have many examples of fossils from millions of years ago surviving?

No, that's the thing about human evolution.

The fossils are very uncommon, generally, except in certain places.

You can count the number of fossils on the fingers of one hand, but the amount of fossils that tell you anything about human origins, you can count on the fingers of one thumb.

They are very, very, very tiny, very scarce, mostly teeth, like mammals generally.

But the thing is that humans in the very broadest sense, meaning all our ancestry going back to apes, were always very rare in the landscape.

I remember going to East Africa to join an expedition looking for fossil humans living 3.3 million years ago in Kenya, and fossils of alligators, catfish, turtles were just so common that you didn't bother collecting them.

Occasionally you would find you know, a little skull of a fossil pig or a bit of a fossil baboon or a bit of an antelope.

But in the entire field season, the the number of fossil human remains were little bits of teeth and jaws that you could fit into a very small biscuit tin.

And that was after months of prospecting.

And that was a good year.

I mean, it's very rare to find a whole skull or even a whole skeleton.

I mean, these are red letter days.

So we are going to be covering several different early human species as this chat goes on.

But with that kind of sparsity of surviving evidence, do we think that there were probably many other species on the human line that we just don't know about?

Oh, absolutely, for sure.

Not only were there likely to be more, but the thing about fossils is fossils is where you find them, and they tend to be more common in some places than others.

So people tend to look in the places where they already know fossils tend to be common.

So

the caves of South Africa have...

you know always had top billing the rift valley of east africa has been a plentiful source.

And people have been looking in other places and finding new things in Southeast Asia, for example.

And there are quite a lot of very mysterious fossils from China.

And places like India have hardly been explored because maybe the relevant rocks are not bound.

West Africa looks likely to be a focus of renewed interest.

There are all sorts of interesting stone tools.

But one of the problems with West Africa, it is covered in forests, which is very untidy for paleontologists who like to look at deserts where the rocks are more exposed.

So there are all sorts of places that people are beginning to look.

And West Africa has some very interesting archaeology.

That is, there's stone tools going back.

And there are beginning to be some surprising results coming out of there.

But the biggest surprises of the past 25 years have been in Southeast Asia, where there are a lot of limestone caves, huge numbers of limestone caves that are barely explored.

And

there is also

now we can look at the whole genome, the whole DNA of modern people, but also the whole DNA of some extinct species, such as Neanderthals and another species called the Denisovans.

We know more about these species from their DNA.

And also we find the DNA, some of the DNA is incorporated into the genes of modern people, such as you and me.

Neanderthals particularly, I think looking at me, I probably have more than you do.

But there are some species, human species, which are only known from bits of DNA in the genomes of living people.

It's a bit like identifying Cheshire cats from their smiles.

And

so

there are more.

Whether we'll discover more is an open question, but there will be more discoveries.

And they do tend to happen rather unexpectedly and not very often right henry now let's delve into the story we are sitting comfortably when does the human story begin we go back to apes i'm presuming yes 10 million years ago cast your mind back if you will to the earth 10 million years ago there were more forests on the earth and we're talking about what we used to call the old world, Eurasia and Africa.

And there were a lot of apes.

There were quite a few apes in Europe and in Africa and in Asia.

But some of these were probably more closely related to gorillas and orangutans than to humans.

But after that period, the forests tend to thin out.

Rather, there was a slow...

In fact, since then, there's been a generally slow cooling of the Earth towards the ice ages.

And in the tropics, the cooling is manifested as forests dying out to be replaced by a more mixed habitat of what you might call savannah or parkland with grasslands and a few trees here and there.

And the number of apes diminished and monkeys became more prevalent.

So there were a few apes hanging on.

But after about 10, 9 million years, the fossil record of apes almost disappears completely.

And so between it until the turn of this century, there was essentially no record of apes or humans or human and possible human relatives between 10 and 5 million years ago.

None, none at all.

And then suddenly in just after 2000, an entire skull dropped right into the middle.

It was about 7 million years ago.

And this came from Chad in Central Africa, which hadn't been very well explored.

And it was an entire skull of a creature called Sahelanthropus Chadensis.

Sahelanthropus.

And it's an unbelievably hard place to work.

I mean, it really does look like a blasted desert.

And people, I've seen people come, I haven't been there, but I have seen people who've come direct to France because it was a French and Chad joint expedition.

I've seen people come back to France directly from Chad without washing and they look yellow.

They look completely sandblasted.

So, but Sahelanthus Chadensis was a whole skull and also there was a couple of elbow joints and a bit of a leg bone that was described later.

And these finds are, they haven't been directly dated, but looking at the, there are lots of other animals found there and looking at the complexion of the fauna, you can tell that it's about seven million years old.

But the interesting thing about Sahelanthropus is it looks like an ape.

The skull's about the same size as chimpanzee, but the hole in the base of the skull where the spinal cord goes in is right in the middle at the bottom or almost rather than at the back and that's crucial because a skull that balances on the spinal cord that's on the bottom it comes from an animal that's a biped it walks on two legs if the hole that the spinal cord goes in is at the back of the skull that suggests that the animal is like your a sheep or your cat or dog.

I have a sheep skull here.

Henry is standing up to fetch the sheep skull, which is right above his office setup.

Here is a skull I prepared earlier.

This is a sheep skull I found when I was nine.

And if you look, that's the hole where the spinal cord would go in.

And it's right at the back of the head.

Right at the back.

It's not, so if you look at the base of the skull, there's the the hole.

It's called the foramen magnum, which is Latin for big hole.

So it's just called a big hole where the spinal cord goes in.

In hominins, that is members of the human family, that hole is moved much further to the centre.

So the skull would balance on top.

And that indicates the one thing that suggests that the owner of the skull was a hominin.

And that means a member of the lineage that led to humans as distinct from our closest relatives, chimpanzees.

And so Sahelanthropus,

that was pretty much the only thing that showed that Sahelanthropus was a hominin.

It looked very ape-like in every other way, but that crucial feature marked it out as closer to living.

It's not an ancestor.

It's not a missing link.

What it means is it is closer to modern humans than to modern apes.

So it is the first sign of something being on our lineage.

a distant great uncle, let's call it.

It's amazing how like the earliest evidence you have, says seven million years ago, found in a remote corner of Chad.

And even though you don't have the full body surviving or all of the legs, just from that skull and the position of the spine, you can deduce that it is different in its locomotion, in bipedality, which is central, isn't it, to the whole story of the rise of humans?

Yes, I mean, it is central.

One of the reasons we can tell is that no other mammal has a skull like that with the foramen magnum underneath.

Bipedality, certainly, of that style is absolutely unique to modern humans.

I mean, there were an awfully long time ago some apes that tried to be bipedal, but they were kind of bipedal in different ways.

They were more definitely apes.

but they all died out a long time ago.

And there's some rather suggestive footprints that are kind of five million years old that

some people think are belong to bipedal creatures some people don't think they're footprints at all and there were apes that lived much longer ago 14 million years or so in there's one called aureopithecus that lived in what is now tuscany that

might have been bipedal but it it died out but this particular mark of bipedality that the hole where the position of the hole in the skull is really what marks marks a hominin, something that is on the human line, as it were, in the human family.

So Sahelanthropus is almost our starting point of examples that we're covering.

And I've got in my notes that this is basically the dawn of the bipedal chimps phase.

So what comes next following Sahelanthropus in the millions of years and in the story of the rise of humanity?

Well, the hominin fossil record being very scant, an awful lot of nothing for another two or three million years.

The record picks up again about five, between five and four million years in East Africa.

There is a creature called Orarin tuganensis from Kenya.

That's not known from the skull at all, but it's known from leg bones, which show a bipedal hominin.

And there is another creature from Ethiopia called Ardipithecus cadaver, which is about nearly five-ish million years ago.

and slightly more recently, Ardipithecus ramidus, which is about four and a half million years old.

Ardipithecus ramidus has most of a skeleton, and that's quite interesting.

I mean, it's a hominin in it.

It shows that the move to bipedality wasn't

a simple linear thing.

Ardipithecus was clearly a hominin and clearly a biped, but not quite as bipedal as you or I.

It was probably much better up a tree.

It would have been a better climber than us.

And it probably, like modern chimps and gorillas do, is they make nests in the lower branches of trees, even though they spend a lot of time on the ground.

So

there are some,

even as late as three and a half million years ago, there are a range of different hominins, the, you know, the bipedal chimp phase.

Some were more bipedal than others.

There is a series of footprints at a a place called Lytoli in Tanzania discovered by Mary Leakey.

This was the great Louis Leakey's wife back at the late 60s.

Did they discover the famous fossil Lucy, Mary Leakey?

No, they didn't.

That was discovered by other people in Ethiopia, but it's generally thought that the species that Lucy's species, Australopithecus afarensis, was the same species that created the footprint at Lytoli.

And certainly from what we know about Lucy's anatomy, that looks perfectly reasonable.

And what we can see from Lucy, because we have a lot of a skeleton of Lucy, what we can see from Lucy and these footprints is that these creatures walked as bipedally as you or I, but there are other footprints at Lytoli.

What happened in Lytoli was three and a half million years ago, there was a volcanic eruption, as there often are in the Rift Valley, and it rained some ash all over the landscape.

and then there was actual rain so the ash became kind of a bit gloopy and muddy and everything walked all over it it looked like the victoria station at rush allower there were the footprints of all sorts of creatures all over it so they're antelopes and pigs and and then there's this famous line of australopithecus afarensis footprints but there were also some footprints of another creature Mary Leakey originally thought it might have been a bear because bears can walk upright.

But this was really just a blind supposition because, you know, fossils of bears are extremely rare.

But it's now thought that this was a different kind of hominin.

There's a foot, a fossil foot that was found in Ethiopia that looked kind of hominin, but it had a much more divergent big toe.

So it's, in other words, its big toe was more like a thumb.

And the footprints made by this mystery,

this mystery hominin might have been made by

that kind of hominin.

So three and a half million years ago, there were bipedal hominins, but some were more bipedal than others.

Lucy, Australophysicus aforensis, walked just like you or I, but probably climbed trees as well.

There's some research to show, some forensic pathology to show that Lucy died when she fell out of a tree.

So she's got fractures consistent with falling out of a tree.

I mean, some people don't believe this, but it's a nice story.

So the bipedal chimp phase had a mixture of different species, some of which were better at climbing than others.

I mean, Henry, it's interesting because obviously we've started with Sahelanthropus and then covered Ardipithecus and then Australopithecus, which feel like the big names you need to cover in that early phase, that bipedal chimp phase.

And yet we've gone from 7 million...

to 3 million years or 3.5 million years.

So that's almost half the whole story of human evolution that we know about.

And yet the evidence that we have surviving is quite rare.

They only know a handful of different species.

Just, for example, that big gap between Sahelanthropus and Ardipithecus that you highlighted between seven and four million years ago.

That's two to three million years in between that the evidence is lacking.

And it'd be fascinating to know kind of, hopefully in the future, more evidence will emerge, learning a bit about that whole evolutionary step, diversity of early bipedal chimp phase.

What could come in the future there?

Well, you know, the thing about paleontology is you must expect the unexpected, so who knows what would come.

But I would imagine that when people start looking, if they find deposits of that of a similar age, they will find a greater variety of the bipedal chimp kind of thing until about two and a half million years ago when things kind of changed a bit.

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And so we get to Australopithecus, and I know with Australopithecus, there are various almost subspecies of Australopithecus found all across Africa.

We're still centered in Africa at this moment in time.

But would you argue, are they the most successful in the bipedal chimp phase?

Are they the most bipedal of them all too?

It's very hard to say because there were quite a few species of Australopithecus.

The first one described, Australopithecus africanus, was described exactly 100 years ago, and that came from South Africa.

So that was Australopithecus africanus.

the paleoanthropology world is celebrating that centenary this

year.

But there were a number of different species, and whether they were all actually different species or not is a matter of very refined argument.

But that genus, Australopithecus, seems to have been pretty successful throughout Africa.

There is another one indeed from Chad, Australopithecus bar-el-ghazali, which is almost it's almost indistinguishable actually from afarensis.

And there there's another one in, there's some more in Ethiopia, Australopithecus, but there were some later ones and there were some slightly different ones.

So there were quite a few of them.

Now, whether there'll be a shakedown and they'll all be the same species or not, or whether there'll be more species, it's very hard to say.

But certainly, as much as anyone has looked, between about five and two and a half million years ago, the Australopithecus model of hominin, which was basically a bipedal chimp, was the kind of hominin that existed on the earth and it's also interesting that yeah so you've got anamensis cediba africanus as you mentioned all these different types of australopithecus just imagining them walking around strutting their stuff maybe the people who left those those footprints at litoli as you mentioned those original footprints found by mary leakey and her team if it seems that these bipedal chimps by the time we get to australopithecus they're becoming more capable of being bipedal and they're almost walking like we we would do at least at some stages the big question is why why do you think these early hominins they start becoming more and more bipedal it's a big question i mean the the question is why did bipedality happen in the first place it's a really unlikely form of locomotion and in my new book which I wanted to call Demure Mindfulness The Taylor Swift Way, but the publishers insisted I called it The Decline and Fall of the Human empire.

I have a whole chapter on bipedality and why it was one of the worst things that could ever have happened to us.

Traditionally, explanations for bipedality, why we got up and stood on two legs, have been of a kind of after-the-fact reasoning.

In other words, we got up on our hind legs to free our hands so we could make tools or carry babies or look over the long grass or

show off our tender genitalia to prospective mates or

any other idea you can you can come up with.

But these don't actually explain the existence of bipodality in the sense that bipodality is far more than getting up on your hind legs.

Various animals can do this, but only for a short time because it's very tiring.

And to be bipedal as a matter of course requires a complete re-engineering of the entire body from the back of the skull, the curvature of the spine, the internal organs, the valves in the veins in our legs, how our feet are constructed, and all sorts of other things.

And bipedality is unbelievably maladaptive.

The reason is that for most of the history of backboned animals, our backbone was evolved about half a billion years ago in an aquatic ancestor.

And basically, it's a kind of clothed line.

It's a kind of clothesline on which the internal organs are hung.

So it's basically a beam that's held horizontally in tension.

And that's great.

But bipeds in the past that were successful, such as dinosaurs, even though they were bipeds, they still held their backbone horizontally.

and they were bipeds because they had a very long tail as a kind of cantilever to the trunk and that allowed them to be bipedal.

But humans don't have tails, so we have to do it the hard way.

We have to stand the whole body up, change the backbone so it's held vertically in compression.

Now, because of this, bad backs are the single most important cause of absenteeism in humans.

The vertical state of humans is responsible for edema in the legs, piles, hernias, glue ear in babies, all sorts of musculoskeletal problems are caused by

bipedalism.

It was a very bad thing.

So how did it evolve?

Well, no one knows, but the current front runner, as it were, is, well, it probably evolved when we were mostly living in trees.

Now, apes and monkeys have a variety of ways of getting around in trees, and one of them is kind of a kind of clambering or climbing.

mode of locomotion where it's called an orthograde posture where the creatures that the creatures basically are climbing in a vertical way among the branches.

So I think bipodality is basically climbing among the branches only without the branches.

And that's the nearest anyone can get to it.

All the other things that have been ascribed to bipodality as an advantage, such as the aquatic ape theory, wading in water or carrying babies or making tools,

these don't require bipodality to happen.

There are lots and and lots of very successful ground-to-living monkeys, such as baboons, that carry their babies quite well and their quadrupeds.

There are monkeys such as capuchins, which are quadrupeds that make tools.

They just sit on their haunches and do it.

Meerkats can stand up and look over the grass and stand on things.

So why bipodality happened?

What good is it for?

Well, it's certainly good for all these things, but it's certainly very bad in many other ways.

Also, it's very disadvantageous if you break a leg.

Now, everyone's seen three-legged dogs running along quite happily, but you know, a one-legged hominin, if you broke a leg, you'd be killed.

You'd be eaten instantly by some animal.

I mean, I broke an ankle in a trivial accident at home a few years ago, and I was only rehabilitated thanks to the National Health Service.

So I was carted off in an ambulance.

I will have the administration of surgeons

anaesthetists and physiotherapists and a wheelchair, a loan from the Red Cross and the long-suffering Mrs.

G to pull me, to push me around in it and a circumstance which definitely led, although she denies it, to her going back to university to qualify as a nurse, specialising in people with learning disabilities, go figure.

But without all these things, I would have died.

So natural selection ensured that when hominins started to be bipedal, they had to get very good at it very quickly.

Otherwise, so once they started to be bipedal, there was no way back.

And so that's why you get all these bipedal hominins around that time.

It's interesting.

It's such a key stage in the story of evolution.

And thank you for explaining that there, Henry.

the importance of that change of the backbone and bipedalism.

So we have got to, let's say, about 3, 2.5 million years ago.

And it feels like this is when the next overarching phase comes in, the beginning of the genus that we belong to, the homo genus, the homo phase begins.

Yes, 2.5 million years ago or thereabouts was a big change in the Earth's climate.

It suddenly began

to get more much cooler and more than it had been and more seasonal.

That's when in the north and far south and in mountain ranges, the ice ages,

the sequences of ice ages began to take hold and become more serious.

And the result of that was in the tropics, the forest shrunk further and something opened up, this tropical grassland called the savannah,

which opened up.

And around that time, two new kinds of hominin appeared.

One was called Paranthropus.

which was a specialist vegetarian.

Now, all hominins before that have been kind of scavengers, omnivores, like chimpanzees today, they would have ate all kinds of things, you know, honey from bees, insects, a bit of plants, nuts, seeds, fruits, maybe some other animals.

Chimpanzees hunt from monkeys, and so they would have eaten a bit of everything.

But Paranthropus became a vegetarian specialist.

It had huge teeth.

and crunched up fibrous nuts and roots.

It's known as the robust one, isn't it?

Or something like that?

Yes,

they have been called robust australopithecines, but they're usually classed in their own genus Paranthropus, and there were several of them.

And life for them started hard and just got harder and harder.

And

they became extinct about half a million years ago.

The other genus was Homo.

That's the genus that includes ourselves.

And the first essays in the genus Homo were probably not much different from Australopithecines.

In fact, some of them called

Homo habilis, Homo Rudolfensis.

There's been an argument that really these are just other Australopithecines.

And I think there's a lot of merit in that.

But the first of the genus Homo that really stood apart was Homo erectus.

And that originated in Africa over two million years ago.

And the reason that was a different thing was it was built entirely differently.

Now, all the Australopithecus and the earliest homo, they had rather short legs and long arms compared with us.

And they didn't have much of a neck.

Their head was quite, you know, stuck onto the body.

And they didn't have a waist.

They had kind of a bit of a pot belly.

And they were good at walking about.

But one thing that Homo erectus could do was run.

And Homo erectus was a specialist meat-eater.

It was a social carnivore, much like hunting dogs.

and probably behaved in the same way.

Now, a friend of mine, Dan Lieberman, and his colleague Dennis Bramble came up with a whole scenario of long distance running as a key feature of the development of homo.

And you know, I'm not surprised Dan is a very keen ultra-marathon runner and runs in bare feet.

So, and he works on human locomotion, so he's really invested in this.

But it's not, it's the whole syndrome.

One thing that Homo has that you don't have except in other predators such as dogs is a ligament that holds the back of the skull to the neck.

So it keeps your head up even without effort.

Another thing is if you have a neck and if you have a waist you can keep running with your arms in contra rotation to your legs.

In other words your left arm moves with your right leg and vice versa and you can keep your neck pointed at where you're looking at whether it's the finish line of the marathon or the antelope you are chasing.

At the same time,

humans became more hairless.

I mean humans have the same amount of hair but it's much sparser and in between there are sweat glands that most other animals don't have i mean your dogs will pant if they're hot and animals such as antelopes and cheetahs and that sort of thing they can run really fast for a short distance and then they have to stop because they become exhausted and they the heat catches up with them but humans Humans can't sprint very well compared with other animals, but humans are much better than many animals at long distance running.

It's the stamina part.

Yeah, it's the stamina, it's the endurance, it's the sweating, it's the hairlessness, it's the fact that the human cost of transport.

In other words, human walking is extraordinarily efficient.

This is why just walking about won't lose you many calories, because it's very, very efficient.

Running is slightly less efficient, but humans can manage it mile after mile after mile after mile.

So

hunter-gatherers, when chasing down some antelope,

will chase it for a bit, but then the antelope will stop and

everyone else will stop and they'll recover.

And then the antelope goes on a bit and the humans chase it.

But the humans are relentless and eventually the antelope will just collapse from heat exhaustion.

And

this is what happens in real life.

And there's also a cooperative element.

because as you find in many carnivals like lions and hunting dogs, they kind of different

different individuals head them off and ambush them, and

one of them flushes it out while the other one jumps on it.

This would have been true for Homo erectus as well.

So, the human syndrome of the human body shape that we associate with humans today came with Homo erectus.

And it seems to have been associated with a capacity for long-distance running that the earlier hominins didn't have, or at least not as well.

Henry, it's no surprise then.

It's no coincidence that Homo erectus literally translates as upright man.

That's correct.

And I remember doing an interview with John McNabb a couple of years ago on Homo erectus, and he showed me a replica pelvic girdle of Homo erectus, and it's basically exactly the same as a modern human.

So as you say, this was a fully bipedal early human built for running, covering long distances, which leads us very nicely into the next big question with Homo erectus, which is how far and wide does Homo erectus ultimately spread?

Because we've been talking only about Africa so far in our chat.

Homo erectus is, as far as we know, the first hominin to spread out of Africa and spread all over Eurasia.

There are tools from China that are over 2 million years old.

There are remains of Homo erectus-like animals or hominins in Spain that are not quite as old.

Now, Homo erectus would have no concept of a continent called Africa or that it was leaving it.

What they were doing was following the game because the savannah spread all through Africa, all through southwestern Asia and into Europe,

right down into Java.

So they were following the savannah.

So, in fact, Homo erectus was first found in Java by Eugene Dubois.

Southeast Asia.

Got it.

Yeah, it was first thought of as a giant gibbon, Pithocanthropus.

And it was only when more of the same kind were found in China that Pithocanthropus and Cynanthropus, as it was, were united into Homo erectus, and they were realized to be much more close to humans.

Another thing that put them fairly close to humans, in certainly in those days, was the discovery that Homo erectus used fire.

Whether they just used opportunistic bits of fire and carried burning bits around, or whether they had learned to actually make fire is a moot point.

So there's some very exciting evidence that I can't tell you about about the earliest, the earliest occurrence of fire starting as opposed to fire usage.

But if I told you that, I'd have to kill you.

So I can't tell you about that.

Not yet.

Next time.

But also, Homo erectus made wonderful stone tools, these teardrop-shaped stone tools called hand axes, which are found all over the eurasia and africa some are small some are big and they're made of different kinds of rock but that is the signature artifact of homo erectus and they may also have scratched scratches on tools on shells there are some shells from eugene dubois excavations in java that show signs of cross hatch scratching and they may also have been capable of some limited water craft because there are remains of Homo erectus homo erectus certainly they're artifacts in islands in island southeast asia that they could not possibly have reached over land even when there were land bridges joining them so homo erectus was quite inventive and widespread but not quite the same as us because you know Alan Walker and Pat Shipman in their book The Wisdom of Bones, which is about Homo erectus, say that if we looked into the eye of one, we wouldn't see a human, we'd see a savannah predator.

They were very much that.

They made tools, but they made tools in a quite different way than we would.

And the reason we know that is nobody knows what a hand axe is actually for.

So, they made hand axes in a very stereotypical way, in the same way that bees make honeycombs or birds make nests.

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Homo erectus is one of, if not the most successful, I would argue, and longest-lasting of early humans, isn't it?

And it's a fascinating story.

If anyone wants to learn more about the story of human evolution, you start at Homo erectus because it is such an essential hominin to learn about and the ultimately the emergence of of homo sapiens and all of that and i wish we could cover so many different examples but henry set the scene just before the arrival of homo sapiens onto the main stage how many different types of early humans are there and how diverse are they yeah homo erectus diversify well you said earlier that in your opinion homo erectus was the most successful hominin and i would completely agree because homo erectus was around from two and a half million and the last ones probably died out maybe 100,000, maybe even more recently in Java.

So almost two and a half million years of very successful history, which is incredibly long time for a mammalian species.

It's generally lived for only a million years.

But by that time, Homo erectus had more or less retired to a comfortable retirement home in Java.

And its successors were all over Europe.

And some of them were big and beefy.

I mean,

Homo heidelbergensis, which is probably not a real species, but a kind of mishmash of other ones, these were big people.

There was a shin bone discovered at Box Grove in Sussex, which is about the size of a large modern male shin bone, but really thick and beefy.

I mean, these people could have played for the British Lions.

I mean, they were big people.

There were some spears, wooden spears, found at Schöningen.

in Germany, about 300,000 years old.

These were fence posts, and yet they were used as weapons.

In East asia a marvellous skull was discovered quite recently there's an amazing story about discovery of homo longi or dragon man ah yes and the skull it's only a skull in the manchuria the skull is at least as big as a modern human so considering that australopithecus was only a meter so tall and with the skull of a chimp you know these people were big i mean you know like Genesis 6 verses 4, maybe it's Genesis 4 verse 6.

I can't remember.

There were giants on the earth in those days.

But there was more.

They were the hobbits.

Homo erectus became marooned on islands in Southeast Asia.

First, it was known in Flores, which is just to the east of Java.

Homo fluisiensis.

And in the Philippines, these creatures became very small.

Because for reasons that nobody really quite understands, big creatures marooned on islands become small and small creatures marooned on islands become big.

So you have these tiny creatures less than three feet tall fighting off gigantic rats the size of dogs and huge komodo dragons and tiny and tiny elephants and the ones in the Philippines fought tiny rhinos and they evolved to be very small but they still made Homo erectus like tools only just smaller and then there was the Neanderthals that they first appeared about 300,000 years ago and the first signs of them are in Spain And they tended to be cave dwellers and they lived in Europe and in Eurasia as far east as Siberia and also you know as far south as the Middle East but they were cave dwellers I think that they were they were built for the rugged extremes of northern Europe in the ice age and they spent most of their time in caves and they cultivated a deep inner life there is a remarkable circular structure in a cave in France that was made by Neanderthals.

It's a structure of broken stalactites and bare skull

that is a circle.

Maybe it was the foundation of some kind of structure, but it was built in a part of the cave that would always have been away from sunlight, always in total darkness.

And

Neanderthals are known to have deliberately buried their dead.

I mean there's some,

there are some early signs of some Neanderthal precursors in the so-called pit of bones at Atapueca

in the Sierra de Atapuerca in northern Spain.

It's a pit of bones because the residents chucked their dead ones down this pit at the back of the cave.

So that was the first sign of any kind of ceremony because when animals die, they don't tend to notice the dead ones very much, except if they're perhaps elephants or some other intelligent creature.

But Neanderthals actually deliberately buried their dead with flowers and other grave markers.

With flowers.

Yes, yes.

There's a very famous Neanderthal grave at Shanidar in what is now Iraq, where there's signs of concentrations of pollen, which suggests that they buried their dead with, they marked their dead with their funeral traditions.

But some Neanderthals, some early Neanderthals looked up at the Tibetan plateau and thought, that looks like a nice place.

And as they climbed, they evolved into these Neanderthal cousins, the Denisophans.

which are Neanderthals.

As far as we know, nobody's found much.

There's a bit of jaw and some teeth and some hand bones, but they're mostly known from their DNA, which has been extracted.

These lived on the roof of the world, which is almost the most inhospitable place you can live, except for Antarctica.

And they evolved into these creatures, the Denisovans.

And we know they evolved at high altitude because

after they evolved at high altitude, they came back down again.

And

traces of their DNA are found in many people who live in East and Southeast Asia to this day.

And a gene from Denisovans is the gene that that allows modern Tibetans to breathe easily at high altitude.

So all these Sherpas who go up and down Everest and don't get the credit, they all have these genes from Denisovans that allow them to breathe in low oxygen tension.

So that was the Denisovans.

So we had these Yetis and we had the troglodytes and we had the hobbits and we had these beefy giants.

All were the heirs of Homo rectus.

And so was Homo sapiens, which originated in Africa Africa at about the same time that Neanderthals originated in Europe.

Yes, Henry, so let's get on to now the final chapter almost, the arrival of Homo sapiens

onto the scene and interactions with all of these other early human species that it must have shared the world with for hundreds of thousands of years before ultimately becoming the last one standing.

Yes, modern humans, Homo sapiens, originated, as far as we know, I mean, the dates keep being put back and back.

The earliest evidence comes from Morocco from a site called Jebel-Ihud, which has been known for a long time.

And every so often, more bones and skulls are dug up.

And the latest news from Jebel-ehud is that there were skulls of something that looked very like Homo sapiens 315,000 years ago or thereabouts.

There are other similar skulls from Ethiopia that look a bit like Homo sapiens, but...

It has to be said that these look pretty rough ingredients.

They didn't look completely like modern humans, so they were

they were probably no better or worse at living in the environment than any other human.

They had to be seasoned by contact with other humans.

Now, the modern view of the origin of Homo sapiens is that groups of Homo sapiens would diverge and then come together again and then diverge again throughout Africa for a very long time.

probably interbreeding with other African hominins whose existence we know very little about, except in their DNA and also the occasional discovery of bones that are very recent in date but look very archaic.

I mean there's a very famous skull from Iho Eluru in Nigeria that's been known for a long time.

It's only 20 something thousand years old but it looks very very archaic and there are other things like that.

So there was a great deal of diversity in Africa, a huge amount of diversity.

And so there were hominins interbreeding with each other to make homo sapiens but at the same time homo sapiens were starting to move out of africa now the first essays in migration in africa were a bit of a failure there is there are there's homo sapiens found in greece that's over 200 000 years ago but it didn't last also

yeah in in what is now israel there's the mount carmel massif where neanderthals and modern humans tended to have a kind of time share arrangement with with all the caves.

In some caves, there are Neanderthals, in some there are modern humans.

And what seems to be the shocker is the modern humans lived there before the Neanderthals did, and they didn't live there that long.

So what happens is modern humans tried to get out of Africa, but the Neanderthals had everywhere else kind of locked up.

So they didn't compete with them very well.

And they probably just visited occasionally in warmer bells of climate.

But things changed because from about 100,000 years ago, maybe slightly more, between 120-ish thousand years ago and 50,000 years ago was quite a warm spell in the Earth's climate.

And that's when modern humans in several waves came out of Africa.

There were two possible routes.

One was through the Sinai Peninsula.

And the other was at the other end of Arabia, the Bab el-Mandeb Straits, which might have been much narrower back in those days.

But one shouldn't get the impression this was a kind of mosaic exodus.

They all kind of decided to go all at once.

I mean, it was in dribs and drabs.

Some were more dribs and drabs than others over a very long period.

But as they went, they met the other hominins, the Neanderthals, the Denisovans, and who knows other ones as well.

And

a lot of the time they made love, not war.

So all modern humans now that do not have an exclusively African descent have about 2% Neanderthal DNA.

It used to be more, but natural selection has weeded out deleterious Neanderthal mutations.

And so it's about 2%.

But we can see evidence for this interbreeding really at the sharp end, because there's a bone of a modern human, a bit of skull of a modern human, about 45,000 years old that's found in...

in Romania that had one Neanderthal great-grandparent.

So you almost get into those hybridizations.

And these hybridizations happened, you know, they weren't often, but they happened enough to leave a strong remnant in our DNA today.

So modern humans got into Europe about 45,000 years ago and drove Neanderthals to extinction within 10,000 years.

Now, why they drove them to extinction is still a matter of contention.

What seems to be the most likely one is you've got to get away from the idea that this all happened all at once.

It took several thousand years to happen.

It took longer than recorded history to happen.

What seems to have happened is that humans, modern humans, were slightly better at raising young to reproductive age than Neanderthals.

Humans were slightly less inclined to inbreed than Neanderthals.

Neanderthals were very inbred.

They lived in much smaller clans than modern humans.

Modern humans ranged slightly further over the landscape than Neanderthals.

Now, all these things at the time were probably too small to notice, but over thousands of years, these things accumulate.

So it got to a point where hominins have always lived in small groups, but the only way to keep up genetic variation and stop people becoming all the same is occasionally to swap mates with other groups.

And what is true in all primates, as far as we know, is that

males tend to stay with the group they were born with, but females tend to move to other groups.

And that's true.

That was true in Australopithecus.

We know this from some amazing work on strontium isotopes in bones, which I won't go into.

But it's also true.

It's also true in humans and the Neanderthals.

So you need that interbreeding.

Clans would often would meet, I guess, at times of festival.

to drink and swap stories and and and worship the great gods and also have marriage ceremonies and choose mates and then they would move around.

But when you get to a point in Europe when there were lots and lots and lots of modern human groups and not many Neanderthal groups, the Neanderthal groups were effectively cut off from other Neanderthal groups.

So there were only two things to do, which is become extinct or interbreed with the humans.

So that seems to have been the case.

It's a similar story in the rest of the world, although not nearly so well documented.

It is known that humans met Denisovans and the Denisovans met Neanderthals in Eastern Asia.

And the same things happened that the only Denisovans survive today in a small percentage of DNA, mostly of people who live in Eastern and Southeastern Asia.

Papua New Guinea is a very good stronghold of modern Denisovan DNA, which is, you know...

who knows it was just the lottery of life the other little ones like the hobbits were probably driven to extinction by humans taking over their range, their resources.

Now it's an interesting thing that the hobbits, the flores, probably disappeared at about the same time that modern humans arrived there, in Flores.

And I have this kind of fanciful notion that folk tales of little people living in the mountains are probably folk memories of previous hominins.

Now, this is just me being completely fanciful, but you know, I'm, as you know, a great fan of Tolkien.

So I think that all the folk tales of elves, dwarves, leprechauns, the little people that lived here before us, might have been a distant folk memory of other hominins that lived in the landscape before we arrived.

But

by 50,000 years ago, all the hominins that had ever lived, and there were many different kinds, had died out except ours.

So do you mean by 40,000?

Do you mean by 40,000 years?

Yeah, it's well, who knows knows exactly?

By about 40,000 years.

Yeah, I suppose so.

Yeah, 50,000 years ago, there were lots and lots of humans.

40,000 years ago, there was just one.

It was just us.

And we lived all over the old world.

And by the end of the last glaciation, modern humans lived from the Arctic to the tropical forests and even had moved into the Americas.

And only Antarctica, Madagascar, and New Zealand and some oceanic islands had not seen the tread of a human foot, but even those would succumb quite quickly.

It makes you realise, also, doesn't it, for those of you listening in from North America or South America, actually how late in the story of human evolution humans do actually cross that bearing land bridge into the Americas, because we focus largely on Eurasia and Africa today.

But that's another...

interesting part of the chat and we've done episodes on the first Americans before.

We've also done an episode with the one and only the oracle of Neanderthal studies, Professor Chris Stringer.

Oh, yeah.

He basically says, quite similar to you, Henry, about, you know, how the Neanderthals die out, that lack of genetic diversity.

And basically, Homo sapiens are just a bit better at all of those important things that endure over time.

I've got a paragraph from your book, which feels good to read out now.

It's only a sentence, actually, a couple of sentences.

As you say, by 40,000 years ago, at the latest, Homo sapiens was the last hominin on Earth.

In just a few geological eye blinks, it had not only eliminated all the other hominins, but had spread to every part of the earth and they say bar madagascar antarctica new zealand and those pacific islands it's a huge journey isn't it having gone from seven million years ago and saw hilanthropus and the first of those bipedal chimps that we know of to homo sapiens to us today

i mean what a journey it has been i mean not for us personally but but the whole story of human evolution

I think the thing that one has to emphasize, though, is that this is not a tale of manifest destiny.

There was nothing written to say that humans would succeed and drive all the other hominins to extinction.

I mean as we've seen, hominins tried to invade Neanderthal territory several times and failed.

And another thing, it's about genetic diversity.

Neanderthals were unbelievably themy genetically.

Now it's known in Neanderthal history that most of them died out sometime in their history.

and that their range was recolonised by other Neanderthals from elsewhere.

Well, the same is true for Homo sapiens.

Humans have always been very, very rare.

They've always been one meal from starvation and two or three meals from extinction.

They always lived in very, very small groups, which tend to be inbred and very thinly scattered over the landscape.

And there have been times, maybe several, where humans have almost died out altogether.

There was an episode about 100,000 years ago, maybe a bit more, when humans almost died out and only lived in refuges in southern Africa.

That's actually quite contentious.

But there is genetic evidence for repeated what's called genetic bottlenecks.

That means that the population shrinks to a tiny, tiny amount and then re-establishes from that tiny, tiny population.

And because there are only a certain amount of genetic variation in that tiny, tiny population, the subsequent population becomes very samey.

Everyone looks very similar because it's built from only a limited amount of genetic variation.

And way back in hominin history, around a million years ago, there's been some recent work published in Science that described what must have been a very awkward age,

about 800,000 years ago, where for a million years there were only about a thousand breeding humans at any one time.

So there was a long period, and this was before Neanderthals.

This was sort of Homo erectus time, but it's talking, it's looking at the genes of people alive today.

There are signs that humans and our immediate ancestors almost became extinct many times.

So the fact that we're alive today is really quite remarkable.

And the fact that we are not only alive today, but we spread throughout the earth with a genetic variability in the entire human species that is no greater than a tribe of chimps living in Côte d'Ivoire today.

So we have this extraordinarily low genetic diversity.

Maybe we succeeded because Neanderthals didn't, it was because their genetic diversity was even worse than ours.

Henry, you do cover that kind of humans today as well in this new book, which is called, it's not the Swiftigeddon book.

Title it is called, Henry?

It is called The Decline and Fall of the Human Empire: Why Our Species is on the Edge of Extinction.

And it's published by Picador in the UK on the 13th of March this year and in America by St Martins Press on the 18th of March.

Well, Henry, it just goes to me to say thank you for coming back on the podcast today.

Thank you very much.

Well, there you go.

There was fan favourite guest, Dr.

Henry G, returning to the ancients to talk through the story of the rise of humans.

I hope you enjoyed the episode.

If you want to listen to the other episodes which feature Dr.

Henry G, well then check out in our archive our episodes on the origins of life on Earth.

There's another one called Top Five Dinosaurs where Henry and I talk through our top five including the brilliant species that was the iguanodon with its thumb spikes and another episode another of Henry's pet favourite topics which is the story of feathered dinosaurs which has really come to the fore in the last couple of decades of scientific research.

Thank you for listening to this episode of the Ancients.

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